The formation of the inclusion complex of PGI.sub.2 -methyl ester with beta-cyclodextrin is a preferred way for stabilizing the PGI.sub.2 methyl ester. The PGI.sub.2 methyl ester content of the complex amounts to 1 to 15% by weight, preferably 3% by weight. By increasing the stability, the effect of PGI.sub.2 methyl ester may be prolonged in several biological systems.
It is known that some prostacyclines have some strong gastric cytoprotective effects. See B. J. R. Whittle et al, Prostaglandine, Vol. 15, A55 (1978). Unfortunately the cytoprotective effect may be used therapeutically, only with difficulty, because of their chemical and biological instability. The active ingredient decomposes easily so that it has to be produced either freshly or else stored under extreme conditions.
It is also known that among other prostaglandin derivatives, the PGE.sub.2 has proved to be significantly effective both in decreasing the blood loss of the gastric mucosa induced by non-steroidal antiphlogistics as well as in the therapy of peptic ulcers. The use of the PGE.sub.2 is, hiowever, difficult because of its diarrhogen side effects.